HTML5 drawImage() method วาดภาพลง Canvas

เพื่อวาดภาพลง canvas ใช้เมธอด drawImage() ของ HTML5:

<!DOCTYPE HTML>
<html>
  <head>
    <script>
      function drawShape() {
        var canvas = document.getElementById('mycanvas');
        if (canvas.getContext) {
          var ctx = canvas.getContext('2d');
          var img = new Image();
          img.src = '/images/backdrop.jpg';
          img.onload = function() {
            ctx.drawImage(img, 0, 0);
            ctx.beginPath();
            ctx.moveTo(30, 96);
            ctx.lineTo(70, 66);
            ctx.lineTo(103, 76);
            ctx.lineTo(170, 15);
            ctx.stroke();
          }
        } else {
          alert('You need Safari or Firefox 1.5+ to see this demo.');
        }
      }
    </script>
  </head>
  <body onload="drawShape();">
    <canvas id="mycanvas"></canvas>
  </body>
</html>